Expansible device for stretching material and method

ABSTRACT

A frame for stretching material secured thereto comprising elongated defining frame elements having mitered ends adapted for juxtapositioning with the confronting end of an adjacent frame element, with rotatable stud means coacting between adjacent frame elements coupling the latter together, and providing for movement of the coupled frame elements relative to one another upon rotation of the stud means for causing stretching of the material attached to the frame. A novel method of stretching material is also disclosed.

United States Patent [191 Johnson Dec. 9, 1975 EXPANSIBLE DEVICE FORSTRETCHING MATERIAL AND METHOD Robert C. Johnson, Pittsburgh, Pa.

[73] Assignee: Metalogic, Inc., Chagrin Falls, Ohio [22] Filed: Nov. 7,1974 [21] Appl. No.: 521,589

[75] Inventor:

[52] US. Cl 38/102.l; 160/374.1 [51] Int. Cl. D06C 3/08 [58] Field ofSearch 160/374, 374.1, 371, 372;

[56] References Cited UNITED STATES PATENTS 375,906 1/1888 Whitmore160/374.l

587,882 8/1897 Tarnke.. 160/3741 1,916,023 6/1933 Shull 160/374!3,448,551 6/1969 Heller 160/374.1 X

3,494,409 2/1970 Prechtl et al. l60/374.l X

FOREIGN PATENTS OR APPLICATIONS 128,867 6/1901 Germany l60/374.l

Primary Exam inerGeo. V. Larkin Attorney, Agent, or FirmBalclwin, Egan,Walling & Fetzer ABSTRACT A frame for stretching material securedthereto comprising elongated defining frame elements having mitered endsadapted for juxtapositioning with the confronting end of an adjacentframe element, with rotatable stud means coacting between adjacent frameelements coupling the latter together, and providing for movement of thecoupled frame elements relative to one another upon rotation of the studmeans for causing stretching of the material attached to the frame. Anovel method of zstretching material is also disclosed.

9 Claims, 10 Drawing Figures US. Patent Dec. 9 1975 3,924,343

FIGB

HPI I Wm EXPANSIBLE DEVICE FOR STRETCHING MATERIAL AND METHOD Thisinvention relates in general to a device and method for stretchingmaterial, such as for instance canvas or other fabric, for use, forinstance, in painting, weaving, decorating or the like, and moreparticularly to an expansible frame wherein rotatable means are providedcoacting between adjacent of the defining frame elements, coupling theframe elements together and providing for predetermined adjustment ofthe frame elements relative to one another upon predetermined rotationof the rotatable means. The device and associated method is adapted foruse by inexperienced individuals and will consistently give uniformresults.

BACKGROUND OF THE INVENTION Various methods and devices for providing ataut surface on fabric-like materials has heretofore been employed. Oneof these prior art methods includes using a generally rigid wood frameand merely pulling the fabric over the frame and then fastening it inplace to the frame, such as for instance by tacks or stapling. Anysubsequent stretching which occurs due to moisture or other causes withsuch prior art arrangement is generally not able to be effectivelycompensated for.

Another prior art method has been to provide a frame member whichembodies wedge means adapted to be driven into each corner of the frameto put desired tension on fabric material secured to the frame. Thismethod likewise does not permit effective further adjustment of thetension on the material after the tension has once been applied by thewedge means, and it is difficult to control the initial tension on thematerial primarily because of the inability to control the tensionimpact on each of the four corners of the frame equally.

Another prior art method has been to use a metallic type frame andsecure fabric material thereto by means of a groove in the metallicframe. Tightening of the fabric material is accomplished by expandingeach of the telescopic-like corners to cause a tension to be applied tothe material. Generally due to the usual lightness of the metallic framemembers, only moderate tightening can be achieved before twisting orbending of the frame occurs.

SUMMARY OF THE INVENTION The present invention provides a frame formedof defining frame elements movable relative to one another, togetherwith readily rotatable adjusting means accessible from exteriorly of theframe, for causing expansion of the frame to thus cause stretching ofattached material.

Accordingly, an object of the invention is to provide a novel device forstretching material secured thereto, for use, for instance, in painting,weaving, decorating or the like.

A further object of the invention is to provide a device of theaforementioned type comprised of a plurality of frame elements havingmitered ends adapted for juxtapositioning with the confronting end of anadjacent frame element, with the confronting ends having aperturestherethrough disposed at generally right angles to the mitered face ofthe respective element, and with rotatable means including bushing meansdisposed in the apertures and stud means extending into the apertures inthe adjacent elements and coacting in force applying relation with thebushing means, for causing relative expansion and contraction movementbetween the adjacentframe elements upon rotation of the stud means,thereby providing for adjustment stretching of material attached to theframe.

A still further object of the invention is to provide a device of theaforementioned type wherein the frame elements may be formed of wood forconvenient attachment of the material to the frame and providing anarrangement which is economical to make and marketable in unassembledkit form, and wherein the device effectively and expeditiously providesfor precise stretching of the material which will give uniform resultsevery time irrespective of the use by inexperienced persons.

A still further object of the invention is to provide a device of theaforementioned type wherein the frame includes corner means for formingthe comers for the frame irrespective of the expansion or contraction ofthe frame elements relative to one another, with the corner meansimparting considerable strength and stability to the frame.

'A still further object of the invention is to provide a novel methodfor stretching material for use for instance in painting, weaving,decorating or the like.

Other objects and advantages of the invention will be apparent from thefollowing description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a bottom plan view of aframe for stretching material constructed in accordance with the presentinvention, and illustrating a piece of material secured thereto;

FIG. 2 is an enlarged, fragmentary, sectional view of one of the cornersof the frame of FIG. 1 with the rotatable means for causing expansionand retraction of the frame elements relative to one another;

FIG. 3 is a view similar to FIG. 2 except that the retatable means hasbeen shown actuated so as to close the frame elements relative to oneanother into engaged relation at their mitered faces;

FIG. 4 is a top or frontal plan view of the frame of FIG. 1, withcertain of the adjustable rotatable means having been actuated to causemovement of the respective frame elements relative to one another;

FIG. 5 is an enlarged, fragmentary, sectional view of one of the ends ofone of the frame elements showing the aperture means therein disposedgenerally perpendicular to the plane of the mitered face of the element;

FIG. 6 is a top plan view of the mitered end of the frame elementillustrated in FIG. 5;

FIG. 7 is a plan view of a piece of material which is adapted forsecurement to the expansible frame and illustrating a particulararrangement including an opening in the material, for insertion of atool therethrough;

FIG. 8 is an enlarged, side elevational view of one of the cornermembers of the expansible frame assembly;

FIG. 9 is an end view taken from the bottom of FIG.

FIG. 10 is an elevational, partially sectioned, illustration of a toolwhich may be conveniently utilized in conjunction with the expansibleframe, for adjusting the rotatable stud means thereof in the operationof stretching material on the frame.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now again to the drawings,there is shown an expansible and retractable material stretching devicecomprising a polygonal shaped frame which includes defining sideelements 12 preferably formed of. wood or some other suitable materialto which stretchable material, such as fabric 14, can be expeditiouslyfastened. In the embodiment illustrated, fastening of the fabric 14 tothe frame 10 is accomplished by means of staples 16 disposed along theperipheral edge of the piece of fabric, and holding the latter inmounted attached condition on the frame 10. While staples have beenillustrated, it will be understood that other suitable fastening meanssuch as for instance adhesive, can be used to fasten material to theframe. If the frame is for weaving, upstanding pins can comprise thefastening means.

The side elements 12 are preferably of sufficient cross sectional areato provide substantial stiffness to the elements, with the elementshaving mitered ends defining end faces 18, which mitered faces areadapted for juxtapositioning with a confronting mitered face of theadjacent frame element, and as shown for instance in FIG. 3. Aperturemeans 20 is provided through each of the ends and extends generallyperpendicular to the plane of the respective mitered face. Such aperturemeans extends from exteriorly of the respective frame element throughthe respective mitered face, and comprises, in the embodimentillustrated, an enlarged diameter opening 22, and a smaller diameteropening 24, axially aligned with opening 22 thereby providing shoulder26 for a purpose to be hereinafter described.

Rotatable means 28 (FIGS. 2 and 3) are provided coacting betweenadjacent frame elements and coupling the latter together. Rotatablemeans 28 comprises in the embodiment illustrated, an elongated stud 30which is threaded adjacent opposite ends thereof as at 30a, 30b, andpreferably having a central nonthreaded knurled section 300, adapted forrotation by the fingers of an individual during assembly of the frameelements 12.

Stud 30 coacts in force applying relation with threaded bushings 32,32a(FIGS. 2 and 3) positioned in the respective aperture means 20 in therespective frame element 12. Thread 30a and associated internallythreaded bushing 32 can be for instance a righthand thread and the otherend of the stud and associated thread internally threaded bushing 32acan be a left-hand thread, so that rotation of the stud 30 in one rotarydirection causes movement of the frame elements toward one another.Rotation of the rotary stud 30 in the opposite rotary direction causesrelative movement of the frame elements 12 away from one another.

Bushings 32,32a are of a lesser length than the length of the respectiveopening 22 in which they are disposed in non-movable relation, with suchbushings engaging the aforementioned shoulder 26 in the associatedaperture means thus positioning the bushing in the aperture means. Aportion of the exterior of each of the bushings may be roughened, as byknurling and as at 33, to prevent rotation when in the respectiveopening 22.

At least one end of the stud 30 is provided with preferably a slot 36(FIG. 2) adapted to receive a tool from exteriorly of the frame, forcausing rotation of the stud and thus relative movem ent between theassociated 4 frame elements 12 as will be hereinafter described indetail.

Each end of each frame element 12 preferably embodies a slot 38 (FIGS. 2and 6) which is adapted to receive therein a portion of a corner member40 (FIGS. 8 and 9) and more particularly the centrally located web 42thereof, for forming a positive corner for the frame irrespective of theexpansion of the frame elements relative to one another duringstretching of the material.

Each of the comer members 40, in the embodiment illustrated, comprisesflange portions 44 disposed in generally V-shaped configuration (FIG. 8)and connected by central web 42. Flange portions 44 are adapted to bereceived in recessed area 46 of the adjacent frame elements, so thatsuch flange portions provide a generally flush continuation of the outerside edge 47 of the respective frame element. Corner portions 40 can bemade of any suitable material, such as for instance, plastic or metal,such as for instance aluminum, and add substantial strength andstability to the frame regardless of the degree of expansion and/orretraction of the frame elements relative to one another.

As can be best seen in FIG. 7, the piece of material 14 is preferably soconfigured at its corners that a tab section 50 thereon will extend overthe respective corner portion and be overlapped by the respective sideportion 52 of the adjacent peripheral edge of the fabric. Since the tab50 is not anchored down by staples or the like, the frame elements canexpand, tensioning the fabric attached to the frame during adjustment ofthe rotatable means 28. The fabric section 14 is preferably providedwith an opening 56 therein which is adapted for alignment with theaperture means 20 in the respective frame element and in generallyoverlying relation with respect to the slot 36 in the associated stud30, so that a tool can be inserted from exteriorly of the frame 10,through the fabric into the aperture means 20, for engaging with theslot in the stud during rotation of the latter, thus applying stretchingforce to the fabric attached to the frame.

It will be seen that merely positioning the fabric with its dotted orprelaid out aligning lines 58 thereon, on the frame, will insure properpositioning of the opening 56 with respect to the aperture means 20, toprovide for proper alignment of opening 56 in the material with theaperture means in the associated frame elements. Lines 58 corresponds tothe side edges of the respective frame element.

Although a conventional screwdriver may be utilized, a tool member 60may be provided for insertion into the aperture means, and intoengagement with the stud 30, for rotating the latter. Such tool in theembodiment illustrated comprises a handle portion 62 having a shankportion 64 rigidly connected thereto, and with the shank portion havinga blade 66 at its distal end, which blade 66 is adapted to be receivedin the aforementioned slot 36 in the respective stud 30, to provide forrotating the latter.

A collar member 68 is axially movable on the shank portion 64 and isadapted for engagement with an abutment 70 on the shank portion and isurged toward the abutment by means of a compression spring 72.

It will be understood that the blade and shank portion are adapted to bereceived into the bushing opening in the respective bushing, so that theblade 66 can engage the slot 36 in the stud 30. Movement of the shankportion 64 and associated blade 66 into the bushing will causeengagement of the collar 68 against the confronting end of the bushing,thereby causing compression of the compression spring 72. Upon releaseof the force applied to the handle, the spring 72 will cause retractionof the shank portion 64 and associated blade 66 from coaction with theslot 36 in the confronting end of the stud 30.

The stretching device of the invention may be conveniently provided inkit form, so that the parts can be readily assembled by anyone who mayhave no particular skill in utilizing the device, and which can bereadily used by anyone with no particular skill and training, forstretching material for use for instance in painting, weaving,decorating and the like. When the kit is opened, the assembler can takethe adjusting stud at the knurled midsection and rotate it so as toengage in threaded coaction with the respective metal bushing in a pairof confronting frame sections. This rotation will cause the two framesections 12 to move toward each other. After the frame members 12 havebeen moved closer together by a few turns of the stud 30 the assemblercan insert a screwdriver or the tool 60 into the aperture in the framemember which contains the slotted end 36 of the stud, for causingrotation of the stud until no further rotation is possible, or in otherwords, when the mitered faces of the two frame members abut tightlytogether, as shown for instance in FIG. 3. Such assembly procedure canthen be repeated for the other unassembled sections of the frame whichcan then be aligned as shown for instance in FIG. 4 and connected bymeans of the associated rotatable means 28.

Prior to attaching the fabric material to the frame the comer tabs orportions 40 can be inserted into each comer. Such comer portions act asa stiffener to give strength to the structure and resist any tendency ofthe frame sections to twist during the stretching process. The corners40 also act to maintain sharp right angle corners which would otherwisebe lost as the stretching process opened gaps between adjacent framemembers. As aforementioned, the material tabs 50 on fabric 14 aids tomaintain corner portions 40 in place.

In assembling the fabric material 14 to the frame 10, the assembler maygrasp the fabric material at the center or any side and fold thematerial over the edge of the adjacent frame element 12. Shoulder 74(FIG. 6) on the back side of the respective frame element aids insecuring the fabric evenly to the frame. The outermost periphery of thefabric can be expeditiously aligned along the back side of theassociated frame element by matching it with a mark on the frameelement. The material positioning process can then be repeated on theopposite side of the frame, and then again on the two remaining frameelements. The assembler can then attach staples 0r tacks progressivelyand alternately outwardly from the first attaching point, with thefasteners disposed along lines running parallel to the respectiveperipheral edge of the material and as shown in (FIG.

1). The assembler can then proceed with stretching of the fabricmaterial if he is using tacks or staples, or if he has used an adhesiveon the fabric, time must expire for the curing of the adhesive, prior tostretching the fabric. It will be seen therefore that assembly of thefabric to the frame becomes a simple matter.

After the unstretched material has been secured to the assembled framethe latter preferably being in the closed condition (FIG. 3), theprocess of stretching may begin. The assembler may insert a screwdriveror the tool 60 through any one of the clearly marked slits 56 cut in thefabric material, and rotate the tool one full turn in a direction sothat relative expansion movement between the adjacent frame elementsoccurs. Such procedure will preferably be repeated successively at eachcorner until the fabric material begins to tighten up and will continueuntil the desired tautness of the material is accomplished. Theassembler can easily check the uniformity of tautness by measuring thewidth of the gap between the adjacent frame elements 12. If it is notthe same at each comer, he knows that the fabric materialis under uneventension, and this may be easily corrected by readjusting the rotatablemeans 28 at any corner. With the use of the device hereinabovedescribed, adjustments can be readily made at any time, and even afterthe assembly is completed, and after the work on the material iscompleted.

From the foregoing description and accompanying drawings, it will beseen that the invention provides a novel device for stretching of fabricmaterial, for use for instance in painting, weaving, decorating or thelike, and wherein the device comprises a frame including elongateddefining frame elements movable relative to one another, with rotatablemeans coacting between adjacent of the frame elements and coupling thelatter together. Predetermined adjustment of the rotatable means causesexpansion of the frame, for causing stretching of the material. Theinvention also provides a novel arrangement of fabric materialstretching frame wherein the rotatable adjustment means includes rightand left hand threads on a rotatable stud coacting in force applyingrelation to bushings embedded in the associated frame element to causerelative movement therebetween. The invention also provides a novelmethod of stretching a material on a frame, and one wherein thestretching process can be precisely and effectively controlled andaccomplished.

The terms and expressions which have been used are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of any of thefeatures shown, or described, and it is recognized that variousmodifications are possible within the scope of the invention claimed.

What is claimed is:

1. A frame for stretching material secured thereto, said framecomprising elongated defining frame elements movable relative to oneanother, and rotatable means coacting between adjacent of said frameelements coupling the latter together, predetermined adjustment of saidrotatable means causing expansion of said frame, for causing stretchingof the material, and wherein said frame elements have mitered end facesadapted for juxtapositioning with the confronting mitered face of anadjacent element, each of said frame elements having an aperturetherethrough disposed substantially at right angles to the respectivemitered face and receiving therein in rotatable relation said rotatablemeans, each of said elements comprising a slot therein at the distal endthereof and receiving therein relatively movable corner means forming acomer for the frame irrespective of the expansion of the frame elementsrelative to one another during stretching of the material, said cornermeans imparting strength and stability to the frame regardless of thedegree of expansion and retraction and the frame elements relative toone another.

2. A frame in accordance with claim 1 wherein said rotatable meansincludes bushing means disposed in said apertures and stud meansextending into said apertures in said adjacent elements and coacting inforce applying relation to said bushing means for causing relativemovement between said adjacent frame elements upon rotation of said studmeans, and means on said rotatable means accessible from exteriorly ofthe respective frame element for causing rotation of said stud means andthus adjustment and relative movement between the confronting ends ofadjacent frame elements.

3. A frame in accordance with claim 2 wherein said apertures eachcomprises a first opening extending generally perpendicular to the planeof said mitered face of the respective frame element and an axiallyaligned second opening greater in diameter than said first opening,extending from exteriorly of the frame element and communicating withthe first mentioned opening, said second mentioned opening being adaptedto receive therein the respective bushing means, while both said firstand second mentioned openings are adapted to receive in generally axialrelation said stud means.

4. A frame in accordance with claim 1 wherein said frame elements areformed of wood for convenient attachment of the material to the frame,and as for instance, by means of staples applied to the frame elementsand material prior to said predetermined adjustment of said rotatablemeans for stretching the material.

5. A frame in accordance with claim 1 wherein said rotatable meanscomprises an elongated threaded stud threaded on opposite ends thereof,means on an end of said stud adapted for engagement with a tool forcausing rotation of the stud, and internally threaded, nonrotatablebushing members disposed in said apertures and coacting in threadedrelation with the respective threaded end of said stud, said bushing atone of said threaded ends comprising a right hand internal thread whilethe bushing at the other of the threaded ends comprises a left handinternal thread, formed complementary to the threads on said stud, sothat rotation of stud in one rotary direction causes adjacent frameelements to move away from one another while rotation of the stud in theopposite rotary direction causes the adjacent frame elements to be drawntoward one another, said means on one end of said stud for rotating saidstud being accessible from exteriorly of at least one of said adjacentframe elements.

6. A frame in accordance with claim 1 wherein said corner meanscomprises a bracket member having a central web adapted to be receivedin the respective slot of the adjacent frame sections and flangesprojecting laterally from said central web, said flanges defining therespective corner of the frame during relative movement between adjacentframe elements of the frame.

7. A frame in accordance with claim 1 wherein said rotatable meanscomprises a threaded stud member threaded at opposite ends thereof andhaving an intermediate non-threaded section separating the threadedsection, one end comprising a right hand thread and the other end ofsaid threaded member comprising a left hand thread, and means on atleast one end of said threaded member for receiving a tool for providingfor tool rotation of said threaded member relative to said frameelements.

8. A frame for stretching materials secured thereto, said framecomprising elongated defining frame elements movable relative to oneanother, and rotatable means coacting between adjacent of said frameelements coupling the latter together, predetermined adjustment of saidrotatable means causing expansion of said frame for causing stretchingof the material, and including comer means coacting between respectiveadjacent frame elements and movable relative to the latter formaintaining stability of the comers of the frame irrespective ofadjustment movement of the frame elements relative to one another uponsaid predetermined rotation of said rotatable means.

9. In a method for stretching material including providing an expansibleand retractable frame comprising elongated defining frame elementsmovably coupled to one another by plural force applying rotatable means,removably securing a piece of stretchable material to the frame elementsalong the latter, at least certain of said frame elements having amitered end defining an end face adapted for juxtapositioning with theconfronting end face of an adjacent frame element, with said mitered endhaving an aperture therethrough disposed at generally right angles tothe mitered end face, said material having an opening therethrough, andaligning said opening in the material with said aperture for actuationof said rotatable means from exteriorly of said frame and through saidmaterial after securing said material to said frame, and inserting ahand tool through said aligned opening and aperture and rotating saidrotatable means from exteriorly of said frame for actuation of saidrotatable means to cause expansion of the frame.

1. A frame for stretching material secured thereto, said framecomprising elongated defining frame elements movable relative to oneanother, and rotatable means coacting between adjacent of said frameelements coupling the latter together, predetermined adjustment of saidrotatable means causing expansion of said frame, for causing stretchingof the material, and wherein said frame elements have mitered end facesadapted for juxtapositioning with the confronting mitered face of anadjacent element, each of said frame elements having an aperturetherethrough disposed substantially at right angles to the respectivemitered face and receiving therein in rotatable relation said rotatablemeans, each of said elements comprising a slot therein at the distal endthereof and receiving therein relatively movable corner means forming acorner for the frame irrespective of the expansion of the frame elementsrelative to one another during stretching of the material, said cornermeans imparting strength and stability to the frame regardless of thedegree of expansion and retraction and the frame elements relative toone another.
 2. A frame in accordance with claim 1 wherein saidrotatable means includes bushing means disposed in said apertures andstud means extending into said apertures in said adjacent elements andcoacting in force applying relation to said bushing means for causingrelative movement between said adjacent frame elements upon rotation ofsaid stud means, and means on said rotatable means accessible fromexteriorly of the respective frame element for causing rotation of saidstud means and thus adjustment and relative movement between theconfronting ends of adjacent frame elements.
 3. A frame in accordancewith claim 2 wherein said apertures each comprises a first openingextending generally perpendicular to the plane of said mitered face ofthe respective frame element and an axially aligned second openinggreater in diameter than said first opening, extending from exteriorlyof the frame element and communicating with the first mentioned opening,said second mentioned opening being adapted to receive therein therespective bushing means, while both said first and second mentionedopenings are adapted to receive in generally axial relation said studmeans.
 4. A frame in accordance with claim 1 wherein said frame elementsare formed of wood for convenient attachment of the material to theframe, and as for instance, by means of staples applied to the frameelements and material prior to said predetermined adjustment of saidrotatable means for stretching the material.
 5. A frame in accordancewith claim 1 wherein said rotatable means comprises an elongatedthreaded stud threaded on opposite ends thereof, means on an end of saidstud adapted for engagement with a tool for causing rotation of thestud, and internally threaded, non-rotatable bushing members disposed insaid apertures and coacting in threaded relation with the respectivethreaded end of said stud, said bushing at one of said threaded endscomprising a right hand internal thread while the bushing at the otherof the threaded ends comprises a left hand internal thread, formedcomplementary to the threads on said stud, so that rotation of stud inone rotary direction causes adjacent frame elements to move away fromone another while rotation of the stud in the opposite rotary directioncauses the adjacent frame elements to be drawn toward one another, saidmeans on one end of said stud for rotating said stud being accessiblefrom exteriorly of at least one of sAid adjacent frame elements.
 6. Aframe in accordance with claim 1 wherein said corner means comprises abracket member having a central web adapted to be received in therespective slot of the adjacent frame sections and flanges projectinglaterally from said central web, said flanges defining the respectivecorner of the frame during relative movement between adjacent frameelements of the frame.
 7. A frame in accordance with claim 1 whereinsaid rotatable means comprises a threaded stud member threaded atopposite ends thereof and having an intermediate non-threaded sectionseparating the threaded section, one end comprising a right hand threadand the other end of said threaded member comprising a left hand thread,and means on at least one end of said threaded member for receiving atool for providing for tool rotation of said threaded member relative tosaid frame elements.
 8. A frame for stretching materials securedthereto, said frame comprising elongated defining frame elements movablerelative to one another, and rotatable means coacting between adjacentof said frame elements coupling the latter together, predeterminedadjustment of said rotatable means causing expansion of said frame forcausing stretching of the material, and including corner means coactingbetween respective adjacent frame elements and movable relative to thelatter for maintaining stability of the corners of the frameirrespective of adjustment movement of the frame elements relative toone another upon said predetermined rotation of said rotatable means. 9.In a method for stretching material including providing an expansibleand retractable frame comprising elongated defining frame elementsmovably coupled to one another by plural force applying rotatable means,removably securing a piece of stretchable material to the frame elementsalong the latter, at least certain of said frame elements having amitered end defining an end face adapted for juxtapositioning with theconfronting end face of an adjacent frame element, with said mitered endhaving an aperture therethrough disposed at generally right angles tothe mitered end face, said material having an opening therethrough, andaligning said opening in the material with said aperture for actuationof said rotatable means from exteriorly of said frame and through saidmaterial after securing said material to said frame, and inserting ahand tool through said aligned opening and aperture and rotating saidrotatable means from exteriorly of said frame for actuation of saidrotatable means to cause expansion of the frame.